Power generation systems typically convert one source of power into electrical energy by turning a rotor of an electrical generator. Power is supplied at a specific voltage and frequency to an electrical grid, which then transmits the power to the consumer. In order to ensure that the power is supplied at a constant voltage and frequency, various control devices/equipment may be used. Ensuring that power is provided at the desired voltage and frequency may be particularly challenging for wind turbine generators, which do not turn the rotor of the generator at a constant speed. The power produced by the turbine must be converted to stable electrical power for transmission.
For example, one prior art wind turbine generator provides a full power converter having a generator side active rectifier coupled to a grid side active inverter via a direct current (DC) link. In this configuration, the active rectifier converts variable frequency alternating current (AC) signals from the generator into a DC voltage, which is placed on the DC link. The active inverter converts the DC voltage on the DC link into fixed frequency AC power for a power grid. Such a configuration requires complicated and expensive circuitry utilizing active switches (e.g., insulated-gate bipolar transistors (IGBTs)) for the active rectifier and inverter. These types of active switches typically have higher power loss during power conversion, and may cause unwanted high frequency harmonics on the power grid.
For example, the grid converter may generate switching frequency harmonics at a frequency of 5 kHz. A grid-side harmonic filter (grid filter) may be used to provide a path for the switching frequency harmonics and prevent the undesired transmission of the switching frequency harmonics to the grid utility. The grid filter may be a capacitor bank that accumulates electrical energy at a variable rate, and discharges the energy at a controlled rate. The grid filter may be connected to the grid side using, for example, a fuse.
One problem associated with currently available wind turbines is that when one or more of the fuses of the grid filter blow, or some other component of the grid filter fails, the grid filter cannot function properly. In some of these currently available systems, when the grid filter fuse blows, there is no feedback signal provided to the wind turbine control system. As a result, the wind turbine will continue to supply power to the grid without the grid filter. This in turn may cause other problems, such as an over-voltage fault alarm or problems connecting to the grid. This problem may be exacerbated in electrical grids that may suffer from poor overall control.
One solution to this problem is to provide various electrical components directly connected to the grid filter to monitor the filter for failures, and report these failures to an operator via the control system. However, in current systems, it may be difficult to find components which are easy to install and service, and which meet various regulatory requirements.
It would therefore be an improvement in the art if a system and method could be developed to overcome one or more of the problems described above.